<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <style>
    .parent {
      position: relative;
      width: 200px;
      height: 200px;
      background-color: lightblue;
      text-align: center;
      line-height: 200px;
    }

    .child {
      position: absolute;
      top: 100%;
      left: 0;
      width: 100%;
      display: none;
      background-color: lightgreen;
      text-align: center;
      padding: 10px;
    }

    .parent:hover .child {
      display: block;
    }

  </style>
  <title>鼠标移入父div显示子div(且移入子div不隐藏，子div为绝对布局)</title>
</head>
<body>
<div class="parent">
  Hover over me
  <div class="child">I'm the child</div>
</div>

</body>
</html>

